Kotlin-reflect QoL APIs (#875)

* Start MoshiKotlinExtensions

* Add Moshi.Builder.add() with reified typeOf

* Use non-shadowing name for addAdapter

* Implement KType.toType()

.javaType isn't implemented

* Don't re-wrap wrapped adapters

* Use new adapter functions in tests to smoke test

* Don't enable uses experimental in kotlin-reflect, only the test

* Use internal leniency API

* Use toType in addAdapter too

* Update error message in test

kotlin/tests/pom.xml

@@ -116,6 +116,7 @@
         <configuration>
           <args>
             <arg>-Werror</arg>
+            <arg>-Xuse-experimental=kotlin.ExperimentalStdlibApi</arg>
           </args>
         </configuration>
       </plugin>